fix: empty tables now respect $env.config.use_ansi_coloring (closes #14896) (#15751)

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- fixes #14896
- related to #15163

# Description
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This PR fixes the presence of ansi color codes in empty tables, when
`$env.config.table.show_empty = true` and `$env.config.use_ansi_coloring
= false`

# User-Facing Changes
Empty tables respect `$env.config.use_ansi_coloring`

# Tests + Formatting
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Added a test for this case.

# After Submitting

crates/nu-command/src/viewers/table.rs

@@ -544,8 +544,13 @@ fn handle_record(input: CmdInput, mut record: Record) -> ShellResult<PipelineDat
     let span = input.data.span().unwrap_or(input.call.head);
 
     if record.is_empty() {
-        let value =
-            create_empty_placeholder("record", input.cfg.width, input.engine_state, input.stack);
+        let value = create_empty_placeholder(
+            "record",
+            input.cfg.width,
+            input.engine_state,
+            input.stack,
+            input.cfg.use_ansi_coloring,
+        );
         let value = Value::string(value, span);
         return Ok(value.into_pipeline_data());
     };
@@ -897,6 +902,7 @@ impl Iterator for PagingTableCreator {
                     self.table_config.width,
                     &self.engine_state,
                     &self.stack,
+                    self.table_config.use_ansi_coloring,
                 );
                 let mut bytes = result.into_bytes();
                 // Add extra newline if show_empty is enabled
@@ -1083,6 +1089,7 @@ fn create_empty_placeholder(
     termwidth: usize,
     engine_state: &EngineState,
     stack: &Stack,
+    use_ansi_coloring: bool,
 ) -> String {
     let config = stack.get_config(engine_state);
     if !config.table.show_empty {
@@ -1098,6 +1105,10 @@ fn create_empty_placeholder(
     let style_computer = &StyleComputer::from_config(engine_state, stack);
     configure_table(&mut out, &config, style_computer, TableMode::default());
 
+    if !use_ansi_coloring {
+        out.table.clear_all_colors();
+    }
+
     out.table
         .draw(termwidth)
         .expect("Could not create empty table placeholder")

crates/nu-command/tests/commands/table.rs

@@ -3847,6 +3847,30 @@ fn table_colors() {
     assert_eq!(actual.out, "╭───┬───╮│ a │ 1 ││ b │ 2 │╰───┴───╯");
 }
 
+#[test]
+fn table_empty_colors() {
+    let actual = nu!("$env.config.use_ansi_coloring = true; []");
+    assert_eq!(
+        actual.out,
+        "\u{1b}[37m╭────────────╮\u{1b}[0m\u{1b}[37m│\u{1b}[0m \u{1b}[2mempty list\u{1b}[0m \u{1b}[37m│\u{1b}[0m\u{1b}[37m╰────────────╯\u{1b}[0m"
+    );
+
+    let actual = nu!("$env.config.use_ansi_coloring = true; {}");
+    assert_eq!(
+        actual.out,
+        "\u{1b}[37m╭──────────────╮\u{1b}[0m\u{1b}[37m│\u{1b}[0m \u{1b}[2mempty record\u{1b}[0m \u{1b}[37m│\u{1b}[0m\u{1b}[37m╰──────────────╯\u{1b}[0m"
+    );
+
+    let actual = nu!("$env.config.use_ansi_coloring = false; []");
+    assert_eq!(actual.out, "╭────────────╮│ empty list │╰────────────╯");
+
+    let actual = nu!("$env.config.use_ansi_coloring = false; {}");
+    assert_eq!(
+        actual.out,
+        "╭──────────────╮│ empty record │╰──────────────╯",
+    );
+}
+
 #[test]
 fn table_index() {
     let actual = nu!(

crates/nu-table/src/table.rs

@@ -16,7 +16,8 @@ use tabled::{
         ansi::ANSIBuf,
         colors::Colors,
         config::{
-            AlignmentHorizontal, ColoredConfig, Entity, Indent, Position, Sides, SpannedConfig,
+            AlignmentHorizontal, ColoredConfig, Entity, EntityMap, Indent, Position, Sides,
+            SpannedConfig,
         },
         dimension::{CompleteDimensionVecRecords, SpannedGridDimension},
         records::{
@@ -228,12 +229,21 @@ impl NuTable {
         self.config.border_color = (!color.is_plain()).then_some(color);
     }
 
+    pub fn clear_border_color(&mut self) {
+        self.config.border_color = None;
+    }
+
     // NOTE: BE CAREFUL TO KEEP WIDTH UNCHANGED
     // TODO: fix interface
     pub fn get_records_mut(&mut self) -> &mut [Vec<NuRecordsValue>] {
         &mut self.data
     }
 
+    pub fn clear_all_colors(&mut self) {
+        self.clear_border_color();
+        self.styles.cfg.set_colors(EntityMap::default());
+    }
+
     /// Converts a table to a String.
     ///
     /// It returns None in case where table cannot be fit to a terminal width.